I'll be watching you - Monitoring is everything

Imagine

Imagine a perfect world, with your perfect system, when everything goes fine.
And fine.
More fine
[...]
And then suddenly you have a call from your boss/client/colleague:

Why our button XYZ is so slow? What's going on?

Then you check:

IIS/apache is fine

Database is fine

JavaScript looks like normal

External functionality is good

So where is the problem? You check XYZ button and it is fine.

So what just happened?

The sad answer: now it is nothing. The problem was 2-3 hours ago and it is gone now. You just spent some of your time completely useless.
The question which suddenly comes to your mind is: what had happened and what changed?
Moreover one more should appear: when it will happen again?

Live dashboards - I know that Zabbix or Nagios are old and ugly, but they are damn useful.

Add more measures to you code with tools like MiniProfiler/Glimpse on .NET or Metric in Java. This can show use easy bottlenecks in our applications. Moreover we can see it live with tools from point 2 and 3.

We are IT, we are lazy, we need tools which will do work for us. Just find what is useful for you and check what your admins use :)

To sum up - remember Sting song :

Every move you make
Every vow you break
Every smile you fake
every claim you stake
I’ll be watching you